This invention relates to a window sash assembly comprising an outer sash formed of metal such as aluminum and adapted to be positioned outdoors, an inner sash formed of adiabatic material such as synthetic resin and adapted to be positioned indoors adjacent the outer sash and a peripheral edge member integral with the indoor end of the inner sash for covering the adjacent open end of an indoor wall member.
In the window sash assembly comprising the outer sash and inner sash, it has been known to form the outer sash of metal such as aluminum and the inner sash of adiabatic material such as synthetic resin to improve the adiabatic property of the sash assembly.
However, when the inner sash is formed of adiabatic material such as synthetic resin, there is the disadvantage that the upper and lower rail frames and the door boxing frames which form the inner sash wear out seriously and lack sufficient durability and also it is impossible to provide an inner sash frmework of sufficient strength.
Furthermore, in the recently developed window sash assembly in which the peripheral edge member is positioned about the indoor end of the inner sash to cover the adjacent open end of the indoor wall member, since the abutment ends of the peripheral edge member must be bevelled at 45.degree. and abut against each other to form a square framework, the inner sash and peripheral edge member are generally formed as separate members.
Examples of the window sash assembly of this type are disclosed in Japanese Utility Model Publications Nos. 2055/1979, and 8002/1979 and Japanese Utility Model Laid-Open No. 109633/1976, for example.
However, when the inner sash and peripheral edge member are formed as separate members, since the two members are required to be separately positioned, it makes the mounting of the window sash assembly in a building window opening inefficient.
Furthermore, since the peripheral edge member is required to be positioned about the inner sash, the area where the peripheral edge member and inner sash contact with each other is visible from the inside (indoors) and dust and/or debris tend to accumulate at the contact area to give an unsightly appearance to the sash assembly.
And as disclosed in Japanese Utility Model Laid-Open No. 87640/1979, the window sash assembly has been known in which the peripheral edge member and inner sash are directly connected together to simplify the mounting operation of the sash assembly in a building window opening. However, in the window sash assembly of this type, when the inner sash is formed of adiabatic material, since the inner sash has insufficient strength, the framework provided by the inner sash and peripheral edge member also has insufficient strength and the framework tends to twist and/or deform when the window sash assembly is installed in a building window opening which makes the installation operation difficult.